Switch to an event allowlist for watchdog

CHANGES.rst

@@ -5,6 +5,8 @@ Version 3.0.5
 
 Unreleased
 
+-   The Watchdog reloader ignores file closed no write events. :issue:`2945`
+
 
 Version 3.0.4
 -------------

src/werkzeug/_reloader.py

@@ -312,7 +312,11 @@ def run_step(self) -> None:
 
 class WatchdogReloaderLoop(ReloaderLoop):
     def __init__(self, *args: t.Any, **kwargs: t.Any) -> None:
-        from watchdog.events import EVENT_TYPE_OPENED
+        from watchdog.events import EVENT_TYPE_CLOSED
+        from watchdog.events import EVENT_TYPE_CREATED
+        from watchdog.events import EVENT_TYPE_DELETED
+        from watchdog.events import EVENT_TYPE_MODIFIED
+        from watchdog.events import EVENT_TYPE_MOVED
         from watchdog.events import FileModifiedEvent
         from watchdog.events import PatternMatchingEventHandler
         from watchdog.observers import Observer
@@ -322,7 +326,14 @@ def __init__(self, *args: t.Any, **kwargs: t.Any) -> None:
 
         class EventHandler(PatternMatchingEventHandler):
             def on_any_event(self, event: FileModifiedEvent):  # type: ignore
-                if event.event_type == EVENT_TYPE_OPENED:
+                if event.event_type not in {
+                    EVENT_TYPE_CLOSED,
+                    EVENT_TYPE_CREATED,
+                    EVENT_TYPE_DELETED,
+                    EVENT_TYPE_MODIFIED,
+                    EVENT_TYPE_MOVED,
+                }:
+                    # skip events that don't involve changes to the file
                     return
 
                 trigger_reload(event.src_path)

tests/test_serving.py

@@ -10,6 +10,7 @@
 from unittest.mock import patch
 
 import pytest
+from watchdog import version as watchdog_version
 from watchdog.events import EVENT_TYPE_MODIFIED
 from watchdog.events import EVENT_TYPE_OPENED
 from watchdog.events import FileModifiedEvent
@@ -136,6 +137,28 @@ def test_watchdog_reloader_ignores_opened(mock_trigger_reload):
     reloader.trigger_reload.assert_not_called()
 
 
+@pytest.mark.skipif(
+    watchdog_version.VERSION_MAJOR < 5,
+    reason="'closed no write' event introduced in watchdog 5.0",
+)
+@patch.object(WatchdogReloaderLoop, "trigger_reload")
+def test_watchdog_reloader_ignores_closed_no_write(mock_trigger_reload):
+    from watchdog.events import EVENT_TYPE_CLOSED_NO_WRITE
+
+    reloader = WatchdogReloaderLoop()
+    modified_event = FileModifiedEvent("")
+    modified_event.event_type = EVENT_TYPE_MODIFIED
+    reloader.event_handler.on_any_event(modified_event)
+    mock_trigger_reload.assert_called_once()
+
+    reloader.trigger_reload.reset_mock()
+
+    opened_event = FileModifiedEvent("")
+    opened_event.event_type = EVENT_TYPE_CLOSED_NO_WRITE
+    reloader.event_handler.on_any_event(opened_event)
+    reloader.trigger_reload.assert_not_called()
+
+
 @pytest.mark.skipif(sys.version_info >= (3, 10), reason="not needed on >= 3.10")
 def test_windows_get_args_for_reloading(monkeypatch, tmp_path):
     argv = [str(tmp_path / "test.exe"), "run"]